Multi-layer photoresist

ABSTRACT

A method includes spin-coating a first metal-free layer over the substrate, depositing a metal-containing layer over the first metal-free layer, spin-coating a second metal-free layer over the first metal-containing layer, forming a photoresist layer over the second metal-free layer, the photoresist layer including a first metallic element, exposing the photoresist layer, and subsequently developing the photoresist layer to form a pattern. The metal-containing layer includes a second metallic element selected from zirconium, tin, lanthanum, or manganese, and the first metallic element is selected from zirconium, tin, cesium, barium, lanthanum, indium, silver, or cerium.

PRIORITY DATA

This application is a continuation of U.S. patent application Ser. No.15/965,417, now U.S. Pat. No. 10,381,481, filed Apr. 27, 2018 andentitled “Multi-Layer Photoresist,” which is hereby incorporated byreference in its entirety.

BACKGROUND

The semiconductor integrated circuit (IC) industry has experienced rapidgrowth. In the course of IC evolution, functional density (i.e., thenumber of interconnected devices per chip area) has generally increasedwhile geometry size (i.e., the smallest component (or line) that can becreated using a fabrication process) has decreased. This scaling downprocess generally provides benefits by increasing production efficiencyand lowering associated costs. However, such scaling down has also beenaccompanied by increased complexity in design and manufacturing ofdevices incorporating these ICs, and, for these advances to be realized,similar developments in device fabrication are needed.

In one exemplary aspect, photolithography (or simply “lithography”) is aprocess used in micro-fabrication, such as semiconductor fabrication, toselectively remove parts of a thin film or a substrate. The process useslight to transfer a pattern (e.g., a geometric pattern) from a photomaskto a light-sensitive layer (e.g., a photoresist layer) on the substrate.Recently, an extreme ultraviolet (EUV) radiation source has beenutilized to provide reduced feature sizes due to its short exposurewavelengths (e.g., less than 100 nm). However, at such small dimensions,roughness of the edges of patterned features has become difficult tocontrol during lithography processes. Accordingly, efforts have beenmade in modifying structures and compositions of photoresist materialsto control such roughness and ensure proper patterning results. Thoughsuch modifications have been generally beneficial, they have not beenentirely satisfactory. For these reasons and others, additionalimprovements are desirable.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is best understood from the following detaileddescription when read with the accompanying figures. It is emphasizedthat, in accordance with the standard practice in the industry, variousfeatures are not drawn to scale and are used for illustration purposesonly. In fact, the dimensions of the various features may be arbitrarilyincreased or reduced for clarity of discussion.

FIGS. 1A, 1B, and 1C illustrate a flowchart of an exemplary methodaccording to various aspects of the present disclosure.

FIGS. 2, 3, 4, 5, 6, 7, 8, and 9 and 12, 13, 14, 15, 16, 17, 18, 19, 20,21, 22, 23, and 24 are fragmentary cross-sectional views of an exemplaryworkpiece at intermediate steps of an exemplary method according tovarious aspects of the present disclosure.

FIGS. 10 and 11 are schematic representations of exemplary chemicalstructures according to various aspects of the present disclosure.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the disclosure.Specific examples of components and arrangements are described below tosimplify the present disclosure. These are, of course, merely examplesand are not intended to be limiting. For example, the formation of afirst feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

In addition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.Moreover, the formation of a feature on, connected to, and/or coupled toanother feature in the present disclosure that follows may includeembodiments in which the features are formed in direct contact, and mayalso include embodiments in which additional features may be formedinterposing the features, such that the features may not be in directcontact. In addition, spatially relative terms, for example, “lower,”“upper,” “horizontal,” “vertical,” “above,” “over,” “below,” “beneath,”“up,” “down,” “top,” “bottom,” etc. as well as derivatives thereof(e.g., “horizontally,” “downwardly,” “upwardly,” etc.) are used for easeof the present disclosure of one features relationship to anotherfeature. The spatially relative terms are intended to cover differentorientations of the device including the features. Still further, when anumber or a range of numbers is described with “about,” “approximate,”and the like, the term is intended to encompass numbers that are withina reasonable range including the number described, such as within +/−10%of the number described or other values as understood by person skilledin the art. For example, the term “about 5 nm” encompasses the dimensionrange from 4.5 nm to 5.5 nm.

The present disclosure relates generally to IC device manufacturing and,more particularly, to device patterning processes using a multi-layerphotoresist structure. Photoresist line edge roughness (LER) and/or linewidth roughness (LWR) plays an increasingly critical role when thedimension of a semiconductor feature decreases to less than 20nanometers. Such roughness in feature morphology may result from factorssuch as, for example, the amount of photon absorbed by the photoresistmaterial and etching selectivity of each material layer underneath thephotoresist material. Though a tri-layered photoresist structureincluding a photoresist layer, a middle layer (e.g., a hard mask layer),and a bottom layer (e.g., bottom anti-reflective coating, or BARC)formed on a substrate has generally demonstrated adequate results,further improvements. Accordingly, the present disclosure provides amulti-layer photoresist structure and corresponding fabrication methodsfor improving feature roughness during lithography patterning processes.

FIGS. 1A-1C illustrate a flowchart of a method 100 for patterning aworkpiece 200 according to some aspects of the present disclosure. Themethod 100 is merely an example, and is not intended to limit thepresent disclosure beyond what is explicitly recited in the claims.Additional operations can be provided before, during, and after themethod 100, and some operations described can be replaced, eliminated,or moved around for additional embodiments of the process. Intermediatesteps of the method 100 are described with reference to cross-sectionalviews of the workpiece 200 as shown in FIGS. 2-9 and 12-24, whileschematic representations of exemplary chemical structures of someembodiments of photoresist materials are shown in FIGS. 10-11. Forclarity and ease of explanation, some elements of the figures have beensimplified.

Referring to block 102 of FIG. 1A and to FIG. 2, the method 100 provides(or is provided with) a workpiece 200 including a substrate 202 forpatterning. The substrate 202 may comprise an elementary (singleelement) semiconductor, such as germanium and/or silicon in acrystalline structure; a compound semiconductor, such as siliconcarbide, gallium arsenic, gallium phosphide, indium phosphide, indiumarsenide, and/or indium antimonide; an alloy semiconductor such as SiGe,GaAsP, AlInAs, AlGaAs, GaInAs, GaInP, and/or GaInAsP; anon-semiconductor material, such as soda-lime glass, fused silica, fusedquartz, and/or calcium fluoride (CaF₂); and/or combinations thereof.

The substrate 202 may be a single-layer material having a uniformcomposition; alternatively, the substrate 202 may include multiplematerial layers having similar or different compositions suitable for ICdevice manufacturing. In one example, the substrate 202 may be asilicon-on-insulator (SOI) substrate having a semiconductor siliconlayer formed on a silicon oxide layer. In other example, the substrate202 may include a conductive layer, a semiconductor layer, a dielectriclayer, other layers, and/or combinations thereof.

The substrate 202 may include various circuit features formed thereonincluding, for example, field effect transistors (FETs), metal-oxidesemiconductor field effect transistors (MOSFETs), CMOS transistors, highvoltage transistors, high frequency transistors, bipolar junctiontransistors, diodes, resistors, capacitors, inductors, varactors, othersuitable devices, and/or combinations thereof.

In some embodiments where the substrate 202 includes FETs, various dopedregions, such as source/drain regions, are formed on the substrate 202.The doped regions may be doped with p-type dopants, such as phosphorusor arsenic, and/or n-type dopants, such as boron or BF₂, depending ondesign requirements. The doped regions may be planar or non-planar(e.g., in a fin-like FET device) and may be formed directly on thesubstrate, in a P-well structure, in an N-well structure, in a dual-wellstructure, or using a raised structure. Doped regions may be formed byimplantation of dopant atoms, in-situ doped epitaxial growth, and/orother suitable techniques.

Referring to block 104 of FIG. 1A and to FIG. 2, the method 100 forms afirst layer 204 over the substrate 202. In many embodiments, the firstlayer 204 is substantially free of any metallic element. In the presentdisclosure, the phrase “substantially free” denotes that a givenmaterial layer comprise an element in a concentration no more than whatis considered for an impurity, such as, for example, less than about 0.1atomic percent. Specifically, the metallic element may be in the form ofa pure metal, a metal compound (e.g., a metal oxide, a metal nitride, ametal oxynitride, a metal silicide, a metal carbide, etc.), a metalalloy (e.g., a combination of multiple metallic elements), or acombination thereof. In one such example, the first layer 204 does notinclude any metallic element (i.e., the concentration of any metallicelement is approximately zero).

In one embodiment, the first layer 204 includes a carbon-rich polymerhaving one of the following structures, where x, y, and z each denotesan integer greater than or equal to 1 and n denotes an integer greaterthan or equal to 2. In a further embodiment, the first polymer 204comprises a mixture of polymers having the following structures.

The first layer 204 may be a bottom anti-reflective coating (BARC) whosecomposition is chosen to minimize reflectivity of a radiation sourceimplemented during exposure of a subsequently-formed photoresist layer.

In another embodiment, the first layer 204 includes a silicon-richpolymer having an exemplary structure as shown below,

where R, R′, R″, R′″, and R″″ are independently selected from aromaticcarbon rings each having 1 to 12 carbon atoms, straight or cyclic alkyl,alkoxyl, fluoro alkyl, fluoroalkoxyl chains each having 1 to 12 carbonatoms, straight or cycicic alkene, alkyne, hydroxyl, ketone, aldehyde,carbonate, carboxylic acid, ester, ether, amide, amine, imine, imde,azide, nitrate, nitrile, nitrite, or thiol functional groups each having1 to 12 carbon atoms, and where x denotes a number of repeating units ofthe structure within the parentheses and may be between 1 and 30. Inmany embodiments, R, R′, R″, R′″, and R″″ are distinctly differentfunctional groups. In one example, R′ may be a chromophore moiety. Inanother example, R″ may be a moiety transparent to the radiation sourceused to expose a subsequently formed photoresist layer. In yet anotherexample, R′″ may be a crosslinking moiety. In a further example, R″″ maybe a monovalent hydrocarbon group. Alternatively, R, R′, R″, R′″, andR″″ may be the same and may each be a hydroxyl group.

In many embodiments, the first layer 204 may be formed by spin-coatingthe carbon-rich polymer and/or silicon-rich polymer described above ontoa top surface of the substrate 202 (or the topmost material layer of amulti-layer substrate 202) and may be formed to any suitable thickness.In some embodiments, the first layer 204 has a thickness of about 50angstrom to about 500 angstrom. In the depicted embodiment, thethickness of the first layer 204 is about 250 angstrom to about 500angstrom. The spin-coating process may be implemented by depositing thecarbon-rich polymer and/or silicon-rich polymer dissolved in a suitablesolvent on the top surface of the substrate 202 followed by orsimultaneously with rotating the substrate 202 to cause the carbon-richpolymer and/or silicon-rich polymer to form a thin film across the topsurface of the substrate 202. The carbon-rich polymer and/orsilicon-rich polymer may be dissolved in any suitable solvent including,for example, n-butyl acetate, methyl n-amyl ketone, 4-methyl-2-pentanol,propylene glycol methyl ether acetate, propylene glycol methyl ether,gamma-butyrolactone, ethyl lactate, cyclohexanone, ethyl ketone,dimethyl formamide, alcohol (e.g., ethanol and methanol), other suitablesolvent, or combinations thereof. Subsequently, the solvent isevaporated by baking (i.e., curing) to form the first layer 204. In manyembodiments, the baking temperature ranges from about 180 degreesCelsius and about 350 degrees Celsius. Other baking temperatures mayalso be suitable for evaporating the solvent.

Referring to block 106 in FIG. 1A and FIG. 3, the method 100 forms asecond layer 206 over the first layer 204. In many embodiments, thesecond layer 206 is a metal-containing layer that includes at least onemetallic element in the form of a pure metal, a metal compound (e.g., ametal oxide, a metal nitride, a metal oxynitride, a metal silicide, ametal carbide, etc.), a metal alloy (e.g., a combination of multiplemetallic elements), or a combination thereof. Non-limiting examples ofthe metallic element include zirconium, lanthanum, manganese, copper,tantalum, tungsten, hafnium, tin, aluminum, titanium, copper, andcobalt. In many embodiments, the second layer 206 is formed by anysuitable process including physical vapor deposition (PVD), chemicalvapor deposition (CVD), atomic layer deposition (ALD), low-pressure CVD(LPCVD), plasma-enhanced CVD (PECVD), and/or other suitable techniques,and may be formed to any suitable thickness. In many embodiments, thesecond layer 206 has a thickness that ranges from about 100 angstrom toabout 250 angstrom. If the thickness of the second layer 206 is greaterthan about 250 angstrom, a pattern subsequently formed in the secondlayer 206 may collapse due to an increased aspect ratio. On the otherhand, if the thickness of the second layer 206 is less than about 100angstrom, a processing window for etching an underlying layer (e.g., thefirst layer 204) may be adversely affected. In some embodiments, thesecond layer 206 has a thickness that ranges from about 20% to about 80%of the thickness of the first layer 204. In the depicted embodiment, thethickness of the second layer 206 is about 100 angstrom to about 200angstrom. Therefore, in comparison to the thickness of the substantiallymetal-free first layer 204, the metal-containing second layer 206 issubstantially thinner, and may provide desired etching selectivity tothe first layer 204 without sacrificing the resolution of the patternduring the etching process.

Referring to block 108 in FIG. 1A and FIG. 4, the method 100 forms athird layer 208 over the second layer 206. In many embodiments, thethird layer 208 is substantially metal-free in a similar manner as thatdiscussed above with respect to the first layer 204. In one example, thethird layer 208 may include a carbon-rich polymer and/or a silicon-richpolymer as described above. In the depicted embodiment, the third layer208 may be formed in a similar fashion as the first layer 204, i.e., bya spin-coating process to any suitable thickness. In the depictedembodiment, the third layer 208 is similar in thickness to the firstlayer 204 and is therefore substantially thicker than themetal-containing second layer 206. In many embodiments, the second layer206 has a thickness that ranges from about 1% to about 70% of thethickness of the third layer 208. The third layer 208 may subsequentlybe baked at a temperature ranging from about 180 degrees Celsius toabout 350 degrees Celsius following the spin-coating process.

Referring to block 110 in FIG. 1A and FIG. 5, the method 100 forms afourth layer 210 over the third layer 208. In many embodiments, thefourth layer 210 includes at least one metallic element in the form of apure metal, a metal compound (e.g., a metal oxide, a metal nitride, ametal oxynitride, a metal silicide, a metal carbide, etc.), a metalalloy (e.g., a combination of multiple metallic elements), or acombination thereof. Similar to the discussion above with respect to thesecond layer 206, the fourth layer 210 may include one or more of thefollowing metal elements: zirconium, lanthanum, manganese, copper,tantalum, tungsten, hafnium, tin, aluminum, titanium, copper, cobalt, orother suitable elements. In some embodiments, the fourth layer 210includes a metallic element that is different from that of the secondlayer 206. In an exemplary embodiment, the fourth layer 210 includes thesame metallic element as the second layer 206. In many embodiments, thefourth layer 210 is formed by any suitable process including PVD, CVD,ALD, LPCVD, PECVD, and/or other suitable techniques, and may be formedto any suitable thickness. In an exemplary embodiment, the fourth layer210 is formed to about the same thickness as the second layer 206 and istherefore substantially thinner than the first layer 204 and the thirdlayer 208. In many embodiments, the fourth layer 210 has a thicknessthat ranges from about 1% to about 70% of the thickness of the thirdlayer 208 or of the first layer 204.

Referring to block 112 in FIG. 1A and FIG. 6, the method 100 forms afifth layer 212 over the fourth layer 210. In many embodiments, thefifth layer 212 is substantially metal-free as discussed above withrespect to the first layer 204 and the third layer 208. In one example,the fifth layer 210 may include a carbon-rich polymer and/or asilicon-rich polymer as described above. In the depicted embodiment, thefirst layer 204 may be a carbon-rich BARC layer, while the fifth layer212 may be a silicon-rich layer. In one such example, the fifth layer212 includes a silicon-rich polymer as discussed with respect to thefirst layer 204. In many embodiments, the silicon-rich polymer includedin the fifth layer 212 may improve adhesion between the underlyinglayers with the subsequently formed photoresist layer (e.g., thephotoresist layer 214). The fifth layer 212 may be formed in a similarfashion as the first layer 204 and the third layer 208, i.e., by aspin-coating process to any suitable thickness. In the depictedembodiment, the fifth layer 212 is similar in thickness to the firstlayer 204 (and the third layer 208) and is therefore substantiallythicker than the fourth layer 210. The fifth layer 212 may subsequentlybe baked at a temperature ranging between about 150 degrees Celsius andabout 500 degrees Celsius following the spin-coating process. In thedepicted embodiment, the first layer 204, the second layer 206, thethird layer 208, the fourth layer 210, and the fifth layer 212, inportion or in entirety, are together considered a composite structure.In some embodiments, one or more of the first layer 204, the secondlayer 206, the third layer 208, the fourth layer 210, and the fifthlayer 212 are optional and may be omitted depending upon specific designrequirements for the workpiece 200 and/or the device from which it isfabricated.

Referring to block 114 in FIG. 1A and FIG. 7, the method 100 forms aphotoresist layer 214 over the fifth layer 212. The photoresist layer214 may be any lithographically sensitive resist material, and in manyembodiments, the photoresist layer 214 includes a photoresist materialsensitive to a radiation source 216 (e.g., UV light, deep ultraviolet(DUV) radiation, and/or EUV radiation as depicted in FIG. 8). However,the principles of the present disclosure apply equally to e-beam resistsand other direct-write resist materials.

The photoresist layer 214 may have a single-layer structure or amulti-layer structure. In one embodiment, the photoresist layer 214includes a resist material (not depicted) that chemically decomposes(and/or changes polarity) and subsequently becomes soluble in adeveloper after the resist material is exposed to a radiation source(e.g., the radiation source 216). Alternatively, the photoresist layer214 includes a resist material that polymerizes (and/or crosslinks) andsubsequently becomes insoluble in a developer after the resist materialis exposed to a radiation source. Notably, the photoresist layer 214provided herein is substantially free of any photosensitive functionalgroups such as, for example, a photo-acid generator (PAG), athermal-acid generator (TAG), a photo-base generator (PBG), aphoto-decomposable base (PDB), a photo-decomposable quencher (PDQ), orother photosensitive functional groups. In the depicted embodiment, thephotoresist layer 214 includes a resist material having a structure 402(referring to FIG. 10), a structure 408 (referring to FIG. 11), or acombination thereof.

Referring to FIG. 10, the structure 402 may be a particle (e.g., acluster) that includes a core group 404 surrounded by multiple ligands412. In the depicted embodiment, dotted lines indicate ionic, covalent,metallic, or van der Waals bonds between the core group 404 and theligands 412. In many embodiments, the core group 404 includes at leastone metallic element in the form of a pure metal (i.e., a metal atom), ametallic ion, a metal compound (e.g., a metal oxide, a metal nitride, ametal oxynitride, a metal silicide, a metal carbide, etc.), a metalalloy (e.g., a combination of multiple metallic elements), or acombination thereof. In many embodiments, the core group 404 includes ametallic element the same as that of the second layer 206 and/or thefourth layer 210, such as, for example, zirconium, lanthanum, manganese,copper, tantalum, tungsten, hafnium, tin, aluminum, titanium, copper,cobalt, or other suitable elements. In an exemplary embodiment, thesecond layer 206 and/or the fourth layer 210 includes one of lanthanum,silver, or cerium, while the core group 404 includes manganese. In someembodiments, the core group 404 may be a metallic oxide (e.g., zirconiumoxide) or a pure metal atom (e.g., tin atom). In other embodiments, thecore group 404 is a positively charged metallic ion. The ligands 412 maybe the same or different from one another and may include a straight orcyclic alkyl, alkoxyl, carboxylic acid, alkene, or other functionalgroups each having 1 to 12 carbon atoms. In the depicted embodiment, thestructure 402 includes the core group 404 and multiple ligands 412(embodiments are not limited to four ligands 412 as depicted in FIG. 10)organized into a particle (i.e., cluster).

Referring to FIG. 11, the structure 408 may be a polymer chaincomprising a backbone 414 and multiple functional groups 416 bondedthereto. The backbone 414 may include any suitable chemical structureand may include one of an acrylate-based polymer, apoly(norbornene)-co-maleic anhydride (COMA) polymer, apoly(hydroxystyrene) polymer, other suitable polymers, or combinationsthereof. In many embodiments, the functional group 416 includes at leastone metallic element in the form of a pure metal (i.e., a metal atom), ametallic ion, a metal compound (e.g., a metal oxide, a metal nitride, ametal oxynitride, a metal silicide, a metal carbide, etc.), a metalalloy (e.g., a combination of multiple metallic elements), or acombination thereof. In the depicted embodiment, the functional group416 includes a positively charged metallic ion bonded to two ligands418. In many embodiments, the functional group 416 includes a metallicelement the same as that of the second layer 206 and/or the fourth layer210, such as, for example, zirconium, lanthanum, manganese, copper,tantalum, tungsten, hafnium, tin, aluminum, titanium, copper, cobalt,other suitable elements, or combinations thereof. In some embodiments,the functional group 416 includes a metallic element such as cesium,barium, lanthanum, cerium, indium, silver, antimony, other suitableelements, or combinations thereof. In the depicted embodiment, thesecond layer 206 and/or the fourth layer 210 includes lanthanum, silver,or cerium, while the functional group 416 includes manganese. Theligands 418 may be the same as or different from one another and mayinclude a straight or cyclic alkyl, alkoxyl, carboxylic acid, alkene, orother suitable functional groups each having 1 to 12 carbon atoms. Insome embodiments, additional functional groups are bonded to thebackbone 414 and/or between the backbone 414 and the functional groups416.

The photoresist layer 214 may be applied by any suitable technique. Insome embodiments, the photoresist layer 214 is applied in a liquid formusing a spin-on (i.e., spin coating) technique. To facilitateapplication, the photoresist layer 214 may include a solvent or amixture of solvents, which when evaporated leaves the photoresist layer214 in a solid or semisolid form (e.g., a film). Non-limiting examplesof solvents include n-butyl acetate, methyl n-amyl ketone,4-methyl-2-pentanol, propylene glycol methyl ether acetate, propyleneglycol methyl ether, gamma-butyrolactone, ethyl lactate, cyclohexanone,ethyl ketone, dimethyl formamide, alcohol (e.g., ethanol and methanol),other suitable solvent, or combinations thereof. The solvent(s) may bedriven off as part of the spin coating, during a settling process,and/or during a post-application/pre-exposure baking process. Thepre-exposure baking process may be implemented by any suitable equipmentsuch as, for example, a hotplate, at any temperature suitable for theparticular compositions of the photoresist layer 214 and the solvent(s)employed.

In other embodiments, the photoresist layer 214 is applied by adeposition method such as, for example, CVD, PVD, ALD, other suitablemethod, or combinations thereof. In one such example, the photoresistlayer 214 may be applied using the same deposition method as thatemployed for forming the second layer 206 and/or the fourth layer 210.

Referring to block 116 of FIG. 1A and to FIG. 8, the method 100 exposesthe photoresist layer 214 to the radiation source 216. In manyembodiments, the radiation source 216 may be an Mine (wavelengthapproximately 365 nm), a DUV radiation such as KrF excimer laser(wavelength approximately 248 nm) or ArF excimer laser (wavelengthapproximately 193 nm), a EUV radiation (wavelength from about 1 nm toabout 100 nm), an x-ray, an e-beam, an ion beam, and/or other suitableradiations. The exposure process 112 may be performed in air, in aliquid (immersion lithography), or in vacuum (e.g., for EUV lithographyand e-beam lithography). In the depicted embodiment, the exposureprocess at block 116 implements a photolithography technique using aphotomask 220 that includes a pattern 218 thereon. The photomask 220 maybe a transmissive mask or a reflective mask, the latter of which mayfurther implement resolution enhancement techniques such asphase-shifting, off-axis illumination (OAI) and/or optical proximitycorrection (OPC). In alternative embodiments, the radiation source 216is directly modulated with a predefined pattern, such as an IC layout,without using a photomask 220 (such as using a digital pattern generatoror direct-write mode). In an exemplary embodiment, the radiation source216 is a EUV radiation and the exposure process at block 116 isperformed in a EUV lithography system. Correspondingly, a reflectivephotomask 220 may be used to pattern the photoresist layer 214.

As depicted in FIG. 9, regions 222 of the photoresist layer 214 exposedto the radiation source 216 undergo chemical changes while unexposedregions 230 remain substantially unchanged in chemical properties. Withrespect to the structures 402 and referring back to FIG. 10, the ligands412 dissociate from the core groups 404 upon being exposed to theradiation source 216, and a larger particle (i.e., structure 420) isformed that comprises multiple core groups 404 and ligands 412surrounding the core groups 404. With respect to the structures 408 andreferring back to FIG. 11, the ligands 418 of different polymer chainscrosslink with each other, effectively forming a network 422 of polymerchains. Accordingly, following the exposure process at block 116, theexposed regions 222 of the photoresist layer 214 undergo polymerizationand/or crosslinking of the resist material and may become less solubleto a subsequently applied developer as a result.

Referring to block 118 of FIG. 1A and to FIG. 12, the method 100performs a developing process on the workpiece 200. The developingprocess dissolves or otherwise removes either the exposed regions 222 orthe unexposed regions 230 depending upon the chemical reactionsundergone in the photoresist layer 214 during the exposure process atblock 116. In the depicted embodiment, the developing process removesthe unexposed regions 230 of the photoresist layer 214. The developingprocess at block 118 may begin with a post-exposure baking process.Depending on the polymer(s) included in the photoresist layer 214, thepost-exposure baking process may catalyze any chemical reactioninitiated by the exposure process at block 116. For example, thepost-exposure baking process may accelerate a cleaving or crosslinkingof the resist material in the photoresist layer 214. Following theoptional post-exposure baking process, a developer (not depicted) isapplied to the workpiece 200, thereby removing particular regions(regions 222 or regions 230) of the photoresist layer 214. Suitableorganic-based developers include n-butyl acetate, ethanol, hexane,benzene, toluene, and/or other suitable solvents, and suitable aqueousdevelopers include aqueous solvents such as tetramethyl ammoniumhydroxide (TMAH), KOH, NaOH, and/or other suitable solvents. In thedepicted embodiment, the developer is an organic solvent. In manyembodiments, a post-exposure bake is performed on the workpiece 200subsequent to the developing process at block 118 to further stabilizethe pattern of the photoresist layer 214.

Referring to block 120 of FIG. 1A and to FIG. 13, the method 100selectively removes portions of the fifth layer 212 using the patternedphotoresist layer 214 as an etch mask. As such, the etching process atblock 120 removes portions of the fifth layer 212 without substantiallyremoving portions of the underlying fourth layer 210, therebydemonstrating etch selectivity for the fifth layer 212 over the fourthlayer 210. The patterned photoresist layer 214 is subsequently removedfrom the workpiece 200 by any suitable method.

Specifically, the fifth layer 212 may be etched using any suitablemethod including a dry etching process, a wet etching process, othersuitable etching process, a reactive ion etching (RIE) process, orcombinations thereof. In an exemplary embodiment, a dry etching processis implemented and employs an etchant gas that includes anoxygen-containing gas (e.g., 02), a carbon-containing gas (e.g.,C_(x)H_(y), where x and y may be any integers), a fluorine-containingetchant gas (e.g., C_(x)F_(y), C_(x)H_(y)F_(z), N_(x)F_(y), and/orS_(x)F_(y), where x, y, and z may be any integers), other suitableetchant gases, or combinations thereof. In the depicted embodiment, themethod 100 performs the dry etching process for less than about 30seconds to remove portions of the fifth layer 212. In many embodiments,an etching bias of less than about 1000 W may be implemented forremoving portions of the fifth layer 212. Alternatively, no etching bias(i.e., 0 W) may be implemented. For embodiments in which the fourthlayer 210 and the photoresist layer 214 both include the same metallicelement (e.g., zirconium, tin, and/or lanthanum), similar etchingresistance afforded by the metallic element may improve patternresolution during the etching of the fifth layer 212, which issubstantially metal-free.

Referring to block 122 of FIG. 1B and to FIG. 14, the method 100selectively removes portions of the fourth layer 210 using the patternedfifth layer 210 as an etch mask. As such, the etching process at block122 removes portions of the fourth layer 210 without substantiallyremoving portions of the underlying third layer 208, therebydemonstrating etching selectivity of the fourth layer 210 over the thirdlayer 208. The patterned fifth layer 212 is subsequently removed fromthe workpiece 200 by any suitable method. In the depicted embodiment,the patterned fifth layer 212 is removed by plasma ashing or flushingusing, for example, oxygen and/or nitrogen plasma. Notably, the methodby which the patterned fifth layer 212 is removed does not substantiallyaffect the underlying patterned fourth layer 210, nor does itsubstantially affect the third layer 208.

In many embodiments, the fourth layer 210, which includes at least onemetallic element, is etched using any suitable method including a dryetching process, a wet etching process, other suitable etching process,an RIE process, or combinations thereof. In many embodiments, a dryetching process is implemented, though the dry etching process forremoving portions of the fourth layer 210 employs different etchant(s)from that implemented for removing the fifth layer 212, which issubstantially metal-free. In one such example, the dry etching processat block 122 employs an etchant gas that includes a chlorine-containinggas (e.g., Cl₂, C_(x)H_(y)Cl_(z), C_(x)Cl_(y), Si_(x)Cl_(y), and/orB_(x)Cl_(y), where x, y, and z may be any integers), abromine-containing gas (e.g., HBr and/or C_(x)H_(y)Br_(z)), anitrogen-containing gas (e.g., N₂), a hydrogen-containing gas (e.g.,H₂), an iodine-containing gas, other suitable gases and/or plasmas, orcombinations thereof. In the depicted embodiment, a chlorine-containinggas is used as an etchant to remove portions of the fourth layer 210,and the method 100 performs the dry etching process for less than about30 seconds. In some embodiments, the dry etching process at block 122 ispreceded by a cleaning procedure for about 10 seconds to about 3minutes.

Referring to block 124 of FIG. 1B and to FIG. 15, the method selectivelyremoves portions of the third layer 208 using the patterned fourth layer210 as an etch mask. As such, the etching process at block 124 removesportions of the third layer 208 without substantially removing portionsof the underlying second layer 206, thereby demonstrating etchingselectivity of the third layer 208 over the second layer 206. Thepatterned fourth layer 210 is subsequently removed from the workpiece200 by any suitable method. In the depicted embodiment, the patternedfourth layer 210 is removed by plasma ashing or flushing using, forexample, hydrogen and/or chlorine plasma. Notably, the method by whichthe patterned fourth layer 210 is removed does not substantially affectthe underlying patterned third layer 208, nor does it substantiallyaffect the second layer 206.

Specifically, the third layer 208, which is substantially metal-free,may be etched using any suitable method including a dry etching process,a wet etching process, other suitable etching process, an RIE process,or combinations thereof. In many embodiments, a dry etching process isimplemented, though the dry etching process for removing portions of thethird layer 208 employs different etchant(s) from that implemented forremoving the fourth layer 210, which includes at least one metallicelement. In one such example, the dry etching process at block 124employs an etchant gas that includes an oxygen-containing gas (e.g.,02), a carbon-containing gas (e.g., C_(x)H_(y), where x and y may be anyintegers), a fluorine-containing etchant gas (e.g., C_(x)F_(y),C_(x)H_(y)F_(z), N_(x)F_(y), and/or S_(x)F_(y), where x, y, and z may beany integers), or combinations thereof. In the depicted embodiment, themethod 100 performs the dry etching process for less than about 30seconds to remove portions of the third layer 208. In many embodiments,the third layer 208 may be etched by a process similar to that describedwith respect to the etching of the fifth layer 212 at block 120.

Referring to block 126 of FIG. 1B and to FIG. 16, the method 100selectively removes portions of the second layer 206 using the patternedthird layer 208 as an etch mask. As such, the etching process at block126 removes portions of the second layer 206 without substantiallyremoving portions of the underlying first layer 204, therebydemonstrating etch selectivity for the second layer 206 over the firstlayer 204. The patterned third layer 208 is subsequently removed fromthe workpiece 200 by any suitable method. In the depicted embodiment,the patterned third layer 208 is removed by plasma ashing or flushingusing, for example, oxygen and/or nitrogen plasma. Notably, the methodby which the patterned third layer 208 is removed does not substantiallyaffect the underlying patterned second layer 206, nor does itsubstantially affect the first layer 204.

In some embodiments, the second layer 206, which includes at least onemetallic element, is etched using any suitable method including a dryetching process, a wet etching process, other suitable etching process,an RIE process, or combinations thereof. In many embodiments, a dryetching process is implemented, though the dry etching process forremoving portions of the second layer 206 employs different etchant(s)from that implemented for removing the third layer 208, which issubstantially metal-free. In one such example, the dry etching processat block 126 employs an etchant gas that includes a chlorine-containinggas (e.g., Cl₂, C_(x)H_(y)Cl_(z), C_(x)Cl_(y), Si_(x)Cl_(y), and/orB_(x)Cl_(y), where x, y, and z may be any integers), abromine-containing gas (e.g., HBr and/or C_(x)H_(y)Br_(z)), anitrogen-containing gas (e.g., N₂), a hydrogen-containing gas (e.g.,H₂), an iodine-containing gas, other suitable gases and/or plasmas, orcombinations thereof. In the depicted embodiment, a chlorine-containinggas is used as an etchant to remove portions of the second layer 206,and the method 100 performs the dry etching process for less than about30 seconds. In many embodiments, the second layer 206 may be etched by aprocess similar to that described with respect to the etching of thefourth layer 210 at block 122. In some embodiments, the dry etchingprocess at block 126 is preceded by a cleaning procedure for about 10seconds to about 3 minutes.

Referring to block 128 of FIG. 1B and to FIG. 17, the method 100selectively removes portions of the first layer 204 using the patternedsecond layer 206 as an etch mask. As such, the etching process at block128 removes portions of the first layer 204 without substantiallyremoving portions of the underlying substrate 202, thereby demonstratingetch selectivity for the first layer 204 over the substrate 202. Thepatterned second layer 206 is subsequently removed from the workpiece200 by any suitable method. In the depicted embodiment, the patternedthird layer 208 is removed by plasma ashing or flushing using, forexample, hydrogen and/or chlorine plasma. Notably, the method by whichthe patterned second layer 206 is removed does not substantially affectthe underlying patterned first layer 204, nor does it substantiallyaffect the substrate 202.

Specifically, the first layer 204, which is substantially metal-free,may be etched using any suitable method including a dry etching process,a wet etching process, other suitable etching process, an RIE process,or combinations thereof. In many embodiments, a dry etching process isimplemented, though the dry etching process for removing portions of thefirst layer 204 employs different etchant(s) from that implemented forremoving the second layer 206, which includes at least one metallicelement. In one such example, the dry etching process at block 128employs an etchant gas that includes an oxygen-containing gas (e.g.,02), a carbon-containing gas (e.g., C_(x)H_(y), where x and y may be anyintegers), a fluorine-containing etchant gas (e.g., C_(x)F_(y),C_(x)H_(y)F_(z), N_(x)F_(y), and/or S_(x)F_(y), where x, y, and z may beany integers), or combinations thereof. In the depicted embodiment, themethod 100 performs the dry etching process for less than about 30seconds to remove portions of the first layer 204. In many embodiments,the first layer 204 may be etched by a process similar to that describedwith respect to the etching of the fifth layer 212 at block 120.

Thereafter, referring to block 130 of FIG. 1B, the method 100 processesthe substrate 202 using the patterned first layer 204 as a mask. Anysuitable method may be performed to process the substrate 202 includingan etching process, a deposition process, an implantation process, anepitaxial growth process, and/or any other fabrication process. Invarious examples, the processed substrate 202 is used to fabricate agate stack, to fabricate an interconnect structure, to form non-planardevices by etching to expose a fin or by epitaxially growing finmaterial, and/or other suitable applications. In the depictedembodiment, referring to FIG. 18, the substrate 202 is etched using thepatterned first layer 204 as an etch mask. The substrate 202 may beetched using any suitable method including a dry etching process, a wetetching process, other suitable etching process, an RIE process, orcombinations thereof. The patterned first layer 204 is subsequentlyremoved using any suitable method such as, for example, by plasma ashingor flushing using oxygen and/or nitrogen plasma.

Referring to block 132 of FIG. 1B, the workpiece 200 may then beprovided for additional fabrication processes. For example, theworkpiece 200 may be used to fabricate an integrated circuit chip, asystem-on-a-chip (SOC), and/or a portion thereof, and thus thesubsequent fabrication processes may form various passive and activemicroelectronic devices such as resistors, capacitors, inductors,diodes, metal-oxide semiconductor field effect transistors (MOSFET),complementary metal-oxide semiconductor (CMOS) transistors, bipolarjunction transistors (BJT), laterally diffused MOS (LDMOS) transistors,high power MOS transistors, other types of transistors, and/or othercircuit elements.

In many embodiments, successive etching of alternating metal-free (e.g.,the first layer 204, the third layer 208, and the fifth layer 212) andmetal-containing layers (e.g., the second layer 206 and the fourth layer210) leads to improved etching selectivity, which may further lead toreduced LWR and/or critical dimension (CD). In an exemplary embodiment,each pair of the alternating layers reduces the LWR by between about 3%and about 20% and the CD by between about 10% and about 20%.Advantageously, the multi-layer photoresist material provided herein mayalso be coupled with other patterning strategies to further reducefeature sizes without compromising pattern resolution.

In one such example, referring to blocks 134 to 146 of the method 100shown in FIG. 1C, a pitch-splitting patterning process is performedafter the pattern 218 is formed in the fifth layer 212 at block 120 ofFIG. 1A. Specifically, referring to block 134 in FIG. 1C and to FIG. 19,the method 100 deposits a layer 240 of spacer material over thepatterned fifth layer 212, which has a pitch 242 (i.e., the smallestdimension between two adjacent features). The spacer material may be anysuitable material including a dielectric material such as an oxide, anitride, an oxynitride, a carbide, or a combination thereof. Notably,the spacer material is substantially free of a metallic element, asilicon-rich polymer, or a carbon-rich polymer such that the spacermaterial may be selective etched during the subsequent processes. Thespacer material may be deposited using any suitable method such as CVD,PVD, ALD, other suitable methods, or a combination thereof.

Referring to block 136 in FIG. 1C and to FIG. 20, the methodanisotropically etches (e.g., by a dry etching process) the layer 240 ofspacer material such that spacers 244 are formed along sidewalls ofmandrels present in the patterned fifth layer 212. Referring to block138 of FIG. 1C and to FIG. 21, the method 100 removes the patternedfifth layer by an etching process similar to that discussed with respectto block 120 of FIG. 1A. In the depicted embodiment, the etching processat block 138 selectively removes the patterned fifth layer 212 withoutsubstantially removing the spacers 244, resulting in a pattern 248having a pitch 246. Because for each mandrel of the pattern 218 twospacers 244 are formed, the pitch 246 is effectively half of the pitch242. Referring to block 140 of FIG. 1C and to FIG. 22, the method 100etches the fourth layer 210 using the spacers 244 as an etch mask. Insome embodiments, the fourth layer 210 may be etched in a similarprocess using similar etchant(s) as those discussed with respect toblock 122 of FIG. 1A.

Subsequently, referring to block 142 of FIG. 1C, the method 100 performsadditional etching processes to the workpiece 200 using the patternedfourth layer 210 as an etch mask to form a patterned third layer 208, apatterned second layer 206, and a patterned first layer 204 (referringto FIG. 23). Subsequently, referring to block 144 of FIG. 1C and to FIG.24, the method 100 processes the substrate 202 using the patterned firstlayer 204 as a mask in, for example, an etching process. Otherfabrication processes may also be applied to the substrate using thepatterned first layer 204 as the mask. Referring to block 146 of FIG.1C, the method 100 performs additional fabrication steps to theworkpiece 200, similar to the discussion above with respect to block 132of FIG. 1B. As such, the final pattern (i.e., the pattern 248) has apitch 246 that is half of that of the original pattern 218, reducing theCD of the features formed on the workpiece 200. Notably, the inclusionof alternating layers of metal-free and metal-containing layers ensurethat LWR of the reduced feature sizes brought about by thepitch-splitting method discussed above may be retained or even improvedduring successive etching processes.

Although not intended to be limiting, one or more embodiments of thepresent disclosure provide many benefits to a semiconductor device and aformation process thereof. For example, embodiments of a multi-layerphotoresist structure including a metal-containing photoresist top layerand alternating layers of metal-free and metal-containing materialsoffers greater control over the lithographic patterning process byimproving the multi-layer structure's sensitivity toward the exposuresource as well as enhancing etching selectivity. As a result,opportunities for tuning and improving LER and/or LWR of IC featureswith reduced sizes may be afforded by embodiments provided herein.

In one aspect, the present disclosure provides a method that includesproviding a substrate, forming a first layer over the substrate, forminga second layer over the first layer, forming a third layer over thesecond layer, forming a photoresist layer over the third layer, exposingthe photoresist layer to a radiation source, and developing thephotoresist layer to form a photoresist pattern.

In some embodiments, each of the first layer and the third layer issubstantially free of any metallic element. In some embodiments, thesecond layer includes a first metallic element, while the photoresistlayer includes a second metallic element. In some embodiments, theexposing of the photoresist layer polymerizes exposed portions of thephotoresist layer.

In some embodiments, the forming of the first layer and the forming ofthe third layer each includes spin-coating a material that issubstantially free of any metallic element, and the forming of thesecond layer includes depositing the first metallic element using one ofchemical vapor deposition, physical vapor deposition, or atomic layerdeposition. In further embodiments, the spin-coating the materialincludes spin-coating one of a carbon-rich polymer or silicon-richpolymer.

In some embodiments, the method further includes baking the first layersubsequent to the forming of the first layer and baking the third layersubsequent to the forming of the third layer.

In some embodiments, the first metallic element and the second metallicelements are the same. In some embodiments, the first metallic elementis zirconium, tin, lanthanum, or manganese.

In some embodiments, the method further includes, prior to forming thephotoresist layer, depositing a fourth layer over the third layer usingone of chemical vapor deposition, physical vapor deposition, or atomiclayer deposition, the fourth layer including a third metallic elementsuch as zirconium, tin, lanthanum, or manganese, and spin-coating afifth layer over the fourth layer, the fifth layer being substantiallyfree of any metallic element. In some embodiment, the fifth layerincludes a silicon-rich polymer.

In another aspect, the present disclosure provides another method thatincludes providing a substrate, forming a composite structure over thesubstrate that includes a first layer formed over the substrate, asecond layer formed over the first layer, and a third layer formed overthe second layer, forming a photoresist layer over the compositestructure, exposing the photoresist layer, developing the photoresistlayer to form a photoresist pattern, preforming a first etching processusing the photoresist pattern as an etch mask to form a patterned thirdlayer, performing a second etching process using the patterned thirdlayer as an etch mask to form a patterned second layer, and performing athird etching process using the patterned second layer as an etch maskto form a patterned first layer.

In some embodiments, each of the first layer and the third layer issubstantially free of any metallic element. In some embodiments, thesecond layer includes a first metallic element, while the photoresistlayer includes a second metallic element. In some embodiments, thesecond layer is silicon-free.

In some embodiments, the first etching process removes portions of thethird layer without substantially removing portions of the second layer.In some embodiments, the second etching process removes portions of thesecond layer without substantially removing portions of the first layer.In some embodiments, the third etching process removes portions of thefirst layer without substantially removing portions of the substrate.

In some embodiments, the performing of the first etching process and thethird etching process each includes implementing one of anoxygen-containing gas, a carbon-containing gas, or a fluorine-containinggas. In further embodiments, the performing of the second etchingprocess includes implementing one of a chlorine-containing gas, abromine-containing gas, a nitrogen-containing gas, or ahydrogen-containing gas.

In some embodiments, the exposing of the photoresist layer isimplemented by applying an extreme ultra-violet radiation source. Insome embodiments, the photoresist layer is substantially free of anyacid-generating moiety. In further embodiments, the second metallicelement is zirconium, tin, cesium, barium, lanthanum, indium, silver, orcerium.

In yet another aspect, the present disclosure provides a method thatincludes spin-coating a first metal-free layer over a substrate,depositing a metal-containing layer over the first metal-free layer,spin-coating a second metal-free layer over the metal-containing layer,forming a photoresist layer over the second metal-free layer, whereinthe photoresist layer includes a first metallic element, exposing thephotoresist layer, and developing the photoresist layer to form aphotoresist pattern. In some embodiments, the method further includes,subsequent to spin-coating each of the first metal-free layer and thesecond metal-free layer, baking each of the first metal-free layer andthe second metal-free layer.

In some embodiments, the first metal-free layer includes a carbon-richpolymer, and wherein the second metal-free layer includes a silicon-richpolymer.

In some embodiments, the metal-containing layer includes a firstmetallic element, the first metallic element being zirconium, tin,cesium, barium, lanthanum, indium, silver, or cerium.

In some embodiments, the metal-containing layer includes a secondmetallic element, the second metallic element being indium, silver, orcerium, and wherein the first metallic element is manganese.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A method comprising: providing a semiconductorsubstrate; forming a first layer over the semiconductor substrate,wherein the first layer includes a first metal; forming a second layerover the first layer, wherein the second layer is substantially free ofany metal; forming a photoresist layer over the second layer, whereinthe photoresist layer includes a second metal; exposing the photoresistlayer to a radiation source; and developing the photoresist layer toform a photoresist pattern.
 2. The method of claim 1, wherein formingthe first layer includes depositing the first metal using one ofchemical vapor deposition, physical vapor deposition, or atomic layerdeposition, and wherein forming the second layer includes spin-coating amaterial that is substantially free of any metal.
 3. The method of claim2, wherein spin-coating includes spin-coating one of a carbon-richpolymer or silicon-rich polymer.
 4. The method of claim 1, wherein thesecond metal is the same as the first metal.
 5. The method of claim 1,wherein the first metal includes zirconium, tin, lanthanum, manganese,or combinations thereof.
 6. The method of claim 1, wherein exposing thephotoresist layer includes applying an extreme ultraviolet (EUV) source.7. The method of claim 1, further comprising forming a third layer overthe semiconductor substrate before forming the first layer, wherein thethird layer is substantially free of any metal.
 8. The method of claim7, further comprising, before forming the photoresist layer: depositinga fourth layer over the second layer using one of chemical vapordeposition, physical vapor deposition, or atomic layer deposition,wherein the fourth layer includes a third metal, the third metalincluding one of zirconium, tin, lanthanum, manganese, or combinationsthereof; and spin-coating a fifth layer over the fourth layer, whereinthe fifth layer is substantially free of any metal.
 9. A method,comprising: forming a first layer over a substrate, wherein the firstlayer is substantially free of any metal; forming a second layer overthe first layer, wherein the second layer includes a first metal;forming a third layer over the second layer, wherein the third layer issubstantially free of any metal; forming a photoresist layer over thethird layer, wherein the photoresist layer includes metal-containingclusters; exposing the photoresist layer; and developing the photoresistlayer to form a photoresist pattern.
 10. The method of claim 9, whereineach of the metal-containing clusters includes a metal-containing coresurrounded by a plurality of carbon-containing ligands.
 11. The methodof claim 10, wherein the metal-containing clusters are firstmetal-containing clusters, and wherein the exposing chemically joinstogether more than one metal-containing core of the firstmetal-containing clusters to form a second metal-containing cluster. 12.The method of claim 9, wherein the metal-containing clusters include asecond metal different from the first metal.
 13. The method of claim 9,further comprising: preforming a first etching process using thephotoresist pattern as an etch mask to form a patterned third layer,wherein the first etching process removes portions of the third layerwithout substantially removing portions of the second layer; performinga second etching process using the patterned third layer as an etch maskto form a patterned second layer, wherein the second etching processremoves portions of the second layer without substantially removingportions of the first layer; and performing a third etching processusing the patterned second layer as an etch mask to form a patternedfirst layer, wherein the third etching process removes portions of thefirst layer without substantially removing portions of the substrate.14. The method of claim 13, wherein performing the first etching processand the third etching process each includes implementing one of anoxygen-containing gas, a carbon-containing gas, or a fluorine-containinggas.
 15. The method of claim 13, wherein performing the second etchingprocess includes implementing one of a chlorine-containing gas, abromine-containing gas, a nitrogen-containing gas, or ahydrogen-containing gas.
 16. A method, comprising: forming a firstnon-metal layer over a substrate; depositing a first metal layer overthe first non-metal layer; forming a second non-metal layer over thefirst metal layer; depositing a second metal layer over the secondnon-metal layer; forming a third non-metal layer over the second metallayer; depositing a third metal layer over the third non-metal layer,wherein the third metal layer includes a metal-containing photosensitivematerial; exposing the third metal layer; and developing the exposedthird metal layer to form a pattern in the third non-metal layer. 17.The method of claim 16, wherein the first non-metal layer includes acarbon-rich polymer, wherein the second non-metal layer includes asilicon-rich polymer, and wherein the third non-metal layer includes acarbon-rich polymer.
 18. The method of claim 16, wherein themetal-containing photosensitive material includes a plurality of polymerchains, such that the exposing polymerizes the plurality of polymerchains.
 19. The method of claim 16, wherein the metal-containingphotosensitive material includes a plurality of clusters, and whereineach cluster includes a metal-containing core surrounded by a pluralityof metal-free ligands.
 20. The method of claim 19, wherein themetal-containing core includes a metal ion.